2.0 Analysis 2.1 Engine Failure The engine lost power when a CT blade failed as a result of the overstress extension of a fatigue-generated crack. The subsequent internal damage to the engine was immediate and catastrophic, causing the compressor section to seize because of vibration and bearing damage. Given the internal damage, the pilot would have been unable to restart the engine. This left the pilot with only one option-to attempt an emergency landing without engine power. 2.2 Pilot Reaction to the Engine Failure It could not be determined why the pilot initially turned right, away from PortAlberni, while declaring the emergency. However, during that manoeuvre, the aircraft's rate of turn increased and the aircraft then rolled out on a heading direct to the PortAlberni Regional Airport. This suggests that the pilot had selected the onboard GPS to display the nearest airports, and then tightened the turn to line up with the PortAlberni Regional Airport. The pilot then requested information to help him avoid high terrain, suggesting that he believed that there could be high terrain on his direct path to the PortAlberni Regional Airport. There is no capability for air traffic controllers to provide such navigational guidance. Additionally, there is currently no requirement for aircraft used in SEIFR operations to be equipped with TAWS. As a result, the pilot would have had no capability to locate or identify obstacles if he entered IMC. The 360 descending turn conducted by the pilot may suggest that the pilot had seen a break in the cloud, and descended through it to maintain visual conditions. That manoeuvre allowed the pilot to avoid flight into cloud below safe IFR altitudes and in an area where he suspected there was high terrain. A post-accident evaluation determined that there were no terrain risks between the aircraft and the airport when the engine failed. The pilot did not know this because the ground was obscured by cloud. Had the aircraft been equipped with a serviceable TAWS, it would have informed the pilot that there were no terrain risks between the point of the engine failure and his intended emergency landing field. With this information, he may have continued with his original plan to fly directly to the PortAlberni Regional Airport rather than descending into a mountainous region to maintain visual reference with the ground. The last radio transmissions from the pilot indicated that he was clear of cloud in visual conditions, and that he had time to identify a potential landing area. He transmitted a Mayday call, and indicated that he was setting up for an emergency landing on a logging road. Because this procedure was being flown in visual conditions, the pilot would have been able to rely on his previous training to accomplish the emergency landing. 2.3 Mean Time Between Failure Calculations The CARs require that engines used for commercial SEIFR operations maintain low MTBF rates. However, the MTBF of the engine may not be the most appropriate indicator of the margin of safety because these calculations do not take into account IFSDs not directly attributable to the engine itself. Regardless of the cause, any system failure that results in a loss of propulsive power leading to an emergency landing represents an elevated risk. Therefore, it would be more appropriate to monitor all SEIFR IFSD events, as is done under rules governing ETOPS operations. 2.4 Equipment SEIFR operations are at increased risk of collision with terrain in mountainous regions where there are generally fewer airfields, unique terrain features, and fewer available sites for off-field emergency landings. The GPS in the aircraft had an expired aviation database. The provision and use of out-of-date information, particularly during an emergency, can lead to an increased risk to flight safety. Many aviation-approved GPS databases do not normally include roads or water bodies or other terrain features that could be useful in identifying potential emergency landing areas in the event that an emergency airfield is not within gliding range. Although equipment is available to display terrain warning information, Canada has no requirement for such equipment to be installed on aircraft engaged in SEIFR operations. When the CAR restriction disallowing SEIFR operations in designated mountainous regions was removed without including a requirement for TAWS equipment, the level of safety to SEIFR operations was significantly reduced. Inclusion of a requirement for TAWS equipment in SEIFR operations would not only increase the margin of safety, but also move to harmonize Canadian regulations with the UnitedStates regulatory environment. 2.5 Routes and Altitudes Published IFR routes are not structured to ensure that available airports remain within the normal power-out gliding range of single-engine aircraft. Unless airline operators are required to evaluate and structure the routes they use for SEIFR operations, the time that this type of flight is exposed to the potential of an emergency off-field landing will remain high. 2.6 Training Although the current regulatory standard (Subsection723.98(24) of the CASS) does require additional pilot training in preparation for SEIFR operations, there is no specific requirement for the simulator and emergency training to include either ground briefing or practice of engine failure/forced landing procedures under instrument flight conditions or in designated mountainous regions. Had the pilot been able to glide the aircraft to the PortAlberni Regional Airport, the forced landing pattern would have had to be accomplished with a ceiling as low as 800feet agl. This type of procedure is not currently practised in simulator or in-flight training. Initial and recurrent training in an approved simulator to cover engine failure procedures in IMC, as well as forced landing procedures under instrument conditions, would better prepare a pilot to respond to such an emergency. The following TSB Engineering Laboratory report was completed: LP 010/2006 - Compressor Turbine Blade Examination This report is available from the Transportation Safety Board of Canada upon request. 3.0 Conclusions 3.1 Findings as to Causes and Contributing Factors The engine lost power when a compressor turbine blade failed as a result of the overstress extension of a fatigue-generated crack. The fracture initiated at a metallurgical anomaly in the parent blade material and progressed, eventually resulting in blade failure due to overstress rupture. The combination of aircraft position at the time of the engine failure, the lack of equipment enabling the pilot to locate and identify high terrain, and the resultant manoeuvring required to avoid entering instrument flight conditions likely prevented the pilot from attempting to glide to the nearest airfield. 3.2 Findings as to Risk Single-engine instrument flight rules (SEIFR) operations in designated mountainous regions have unique obstacle risks in the event of an engine failure. Canadian equipment requirements for such operations do not currently include independent terrain mapping, such as terrain awareness and warning systems (TAWS). Airline operators are not currently required to conduct any additional route evaluation or structuring to ensure that the risk of an off-field landing is minimized during SEIFR operations. Pilots involved in commercial SEIFR operations do not receive training in how to conduct a forced landing under instrument flight conditions; such training would likely improve a pilot's ability to respond to an engine failure when operating in instrument meteorological conditions (IMC). Mean time between failure (MTBF) calculations do not take into account In Flight Shut Downs (IFSDs) not directly attributable to the engine itself; it may be more appropriate to monitor all IFSD events. The design of the Cessna 208B Caravan fuel shutoff valves increases the risk that the valves will open on impact, allowing fuel spillage and increasing the potential for fire. 3.3 Other Finding Sonicblue Airways was not providing downloaded engine parameter data for engine condition trend monitoring (ECTM) evaluation at appropriate intervals. 4.0 Safety Action 4.1 Action Taken 4.1.1Terrain Awareness and Warning System Equipment Requirement A requirement for the installation and use of terrain awareness and warning systems (TAWS) has been supported by Transport Canada (TC). This installation and use of TAWS equipment will enhance a pilot's ability to identify and avoid terrain risks in the event of a loss of propulsion under instrument meteorological conditions (IMC). Information about the TAWS equipment requirements that are being approved for Canada can be found in TC's Commercial and Business Aviation Advisory Circular 0236 dated 29 July 2005, which is available on the TC website. 4.1.2 Enhanced Pilot Training Requirement On 06 June 2007, the TSB sent a Safety Advisory to TC suggesting that TC consider incorporating additional pilot training requirements into Subsection 723.98(24) of the Commercial Air Service Standards (CASS) to ensure that single-engine instrument flight rules (SEIFR) pilots receive practical training on engine failure procedures in IMC. The training would include the pilot's initial response to the failure, the descent in instrument conditions, the avoidance of terrain hazards during the descent, and the practice of forced landings under various degraded surface weather conditions. TC responded to this Safety Advisory on 25 July 2007. The response outlined a number of difficulties involved in establishing a specific standard that could cover a myriad of circumstances that a pilot may meet in the event of an engine failure under SEIFR operations. TC's position is that air operators should be proactive in reviewing their SEIFR operations, specific to their individual training program, to ensure that this possible training gap or related hazard is addressed within the company operations manual. TC's Civil Aviation Standards Branch will prepare an issue paper with the recommendation that air operators review their company training programs to ensure that SEIFR pilots receive practical training on engine failure procedures in IMC specific to the air operator operations and geographic location. 4.2 Action Required 4.2.1 Propulsion System Reliability SEIFR authorization is based in part on the improved reliability of turbine engines as compared to piston engines. An essential element for SEIFR approval is that mean time between failure (MTBF) of the engine must remain high. Canadian Aviation Regulations (CARs) require the MTBF of the engine to be better than 0.01per 1000hours (that is, less than 1failure per 100000hours of flight time). Other Canadian-approved flight operations such as extended range twin-engine operations (ETOPS) are authorized in part because of the increased reliability of modern turbine engines. ETOPS are governed by TP6327, Safety Criteria for Approval of Extended Range Twin Engine Operations (ETOPS). Appendix A of that publication recognizes that: No single parameter by itself, without other data/information, can adequately qualify reliability. There are a number of variables, maintenance and operating statistics and general information about the operational experience of a particular power unit, which characterize propulsion system reliability. To ensure the reliability of propulsion systems used for ETOPS, TP6327 requires a record of all engine shutdown events both ground and in flight for all causes (excluding normal training events) including flameout. It also requires a list of all occurrences where achieved thrust was below the intended level, for whatever reason. Although many of the rules governing ETOPs cannot be applied directly to single-engine operations, the underlying concept used to monitor propulsion system reliability could be applied to SEIFR to ensure a similar level of safety for crews and passengers. While the engine type that was involved in this accident met the established reliability standard, it is important to note that, had the total number of In Flight Shut Down (IFSD) events (that is, loss of propulsion for all causes) been considered, the failure rate for the entire propulsion system would not have met the CARs standard in 7 of the last 10years. Any system failure that results in a loss of power and an emergency landing represents an elevated risk to the travelling public. Because the outcome of an engine failure in SEIFR operations can be catastrophic, the propulsion system reliability assessment should take into account all relevant variables and should not be limited to MTBF values alone. Therefore, the Board recommends that: The Department of Transport take into account all propulsion system failures when assessing the safety of single-engine commercial operations. A07-08 Assessment Rating: Satisfactory Intent